Comment by samiv

For the developer that knows what they're doing the installer is not absolutely necessary, you can just download the zip (or tar.gz) and extract the whole thing somewhere and go from there. The installer does provide some more advanced features such as selecting feature by feature and version by version which Qt components you want to install. At least this is how it works on Windows, I expect Mac to behave similarly.

For the end user of your product you'd of course package your software with the Qt libs (or integrate the Qt installation process in your application installation process) so that the end user doesn't need to know nor care about Qt installation at all.